Though Some Tasks Are Just Beyond a Child's Reach, Children

Though some tasks are just beyond a child's reach, children receiving appropriate guidance from skilled partners can make rapid progress. According to Vygotsky, when are interactions like this most helpful?

A) when they take place within a child's zone of proximal development
B) when they take place within a child's zone of vicarious learning
C) when they take place within a child's zone of cognitive development
D) when they take place within a child's zone of intrinsic motivation